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Model Output Discussion 29th December - Into mid-Winter.


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8 minutes ago, Ice Day said:

At 234 it's pushing heights up towards Scandi.  Who knows where FI is going on this run, I think the pub run has found the 1982 bottle of whisky at the back of the larder!

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The Hooker is in place but there are no props.

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Evening All For those of us who have been here for a long while there is times when you know you have to throw in the towel on chasing cold & times ( very rare ) when you 'just know' that the

Boom goodnight vienna

People being a bit harsh on Steve Murr, at least he has the balls to try and read and predict what may happen from his viewpoint rather than just posting what charts show.

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3 minutes ago, Frosty. said:

Very interesting charts for next Saturday with snow across Wales, the midlands and parts of the south. I'm really looking forward to this cold outbreak, I know we have had some cold quiet weather but this should be exciting with a good chance of snow for most of the uk for the FIRST time this winter!:D

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Any chance we may get a smidging down west?

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6 minutes ago, johnholmes said:

Turning to the realistic time scale, what more do folk want than this Fax for 120h. Yes it may change but it is probably more reliable than any of us on here trying to suggest waht the flow might be.

http://www.weathercharts.org/ukmomslp.htm#t120

Direct from santa land, time to start watching the weather reports from Jan Meyen then Thorshave to get an idea of the T and Td values. Any minor troughs will enhance shower activity giving the probability of it well inland from the coasts. Possible development of one or more actual lows (may be Polar Lows) which would enhance even more. So lots for the coldies to be upbeat about instead of worry yet again at the outer realms of GFS.

That train of troughs following the 528 DAM line @120 could cause Knocker's mate to go into hibernation, at last.

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47 minutes ago, PerfectStorm said:

Snow for midlands next saturday :wink:

gfs-2-168.png?18

For goodness sake another run with a warm sector = 'rain day' Saturday.

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4 minutes ago, mountsbaysnow said:

Any chance we may get a smidging down west?

I think anywhere in the uk could see some wintry ppn later next week, even the woodshed in Cornwall is not to be ruled out. It looks like a cold snap / outbreak is on the way, duration and strength still unclear but it's the most interesting spell of the winter so far we are looking at.

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According to the Control, a decent snow event for most of the country on Thursday night.  Further North and West you are the better, but details will change as we count down of course.

gens-0-2-120.png

This is now down to 120 hours!

 

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Looking at the GEFS 18z mean...cold wintry spell later next week looks locked and loaded!:cold-emoji:

Some of us are likely to see a covering of snow soon:D

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2 hours ago, Steve Murr said:

Well all I can say is yes it may not happen however if you look at the change in the last 24 hours from the 216 mean yest to the 192 mean today you will see that the clustering must have shifted towards cold ( hence why I posted it ) 

yest 216

 

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today 192

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also a very crude measure of why the scandi high means get muted

if we have 35 members with a 1040 MB high over scandi & just 15 rogue members that are flat & have a deep 980MB low over scandi at the same time them the mean pressure at day 10 will be 1022 MB -& the contour lines will look significantly flatter as a result...

Its all about clusters if you want to use the mean & the clusters have shifted more to cold tonight ....

 

Excellent post - the obsession with mean runs (which I haven't noticed in prior years) in FI seems very odd to me.  As an Economist looking at data distributions and describing them by mean without a dispersion measure seems pointless.  Even with a dispersion measure you would still want to see skew.  From my perspective all these charts give you is a very broad brush trend of all the ensembles.  When you look at the dispersion patterns in FI they are so vast. Median would be a better measure given how most people use them.  There are dispersion measures using standard deviation which give a good idea of how well the op is supported relative to ensemble mean.  Nick F posted one back on page 168.  I'd like to see much more of this data being posted on the model thread.  The charts he posted showed exactly where the models had the greatest variability in the northern hemisphere.  We have a lot of data produce by the models but this measure goes under reported on the forum.  Essentially it's telling us where the models are solid and where they are uncertain.  Nick F if you could post more (or let me know where they can be found) that would be great.

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59 minutes ago, radiohead said:

18Z GFS op was an off-the-scale outlier in terms of pressure south of Greenland on the 15th. 

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Agreed, although it does look like the trend is for the pressure to drop, just not as far.

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22 minutes ago, ArHu3 said:

I don't think I have ever seen such narrow bandwidth for so far into the future before

Screenshot 2017-01-08 01.40.04.png

Quite a bit colder in the SE of Holland too. I'm wondering how far south and west this can go - maybe all the way down here given the suggested longevity in the ensemble.

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Fantastic ECM run upto 144 hours, low thicknesses, unstable clean flow with frequent blustery wintry(snow) showers and snow falling quite widely at lower levels in North Western areas although almost anywhere could see snow falling at some point.

I'm not sure where the talk of its only going to be a toppler with just snowfall confined to the hills is coming from tbh, low thicknesses tend to come with a lower DAM point and therefore lower dewpoints, low thicknesses also causes deeper convective potential and much to my surprise the flow is looking very 'clean' at least initially before shortwaves do start to come into play.

Hopefully there won't be any significant downgrades in terms of the initial cold NW'ly blast and what happens after that remains very much uncertain. Just hope the UKMO is right regarding the amplification in the short term as that gives us the best chance for this NW'ly to deliver the best potential.

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This little system could give a proper snow event in the SW, shame it come through during the day as that could make the difference on settling etc...

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